i would advice maybe getting it checked out allergies can be in certin parts of your body, and because its very close and gets wet its more likely to cause rash or such, the liners can be bought in most places, i wouldn;t advice using anymore material as you are unsure whats causing this, i would talk to your doctor, it might even be thrush, my son had this pretty awful when he was little i thought it was either nappy rash or allergy.